In Situ Constructed Perovskite–Chalcogenide Heterojunction for Photocatalytic CO₂ Reduction

Abstract

Perovskite nanocrystals (PNCs) are promising candidates for solar‐to‐fuel conversions yet exhibit low photocatalytic activities mainly due to serious recombination of photogenerated charge carriers. Constructing heterojunction is regarded as an effective method to promote the separation of charge carriers in PNCs. However, the low interfacial quality and non‐directional charge transfer in heterojunction lead to low charge transfer efficiency. Herein, a CsPbBr3–CdZnS heterojunction is designed and prepared via an in situ hot‐injection method for photocatalytic CO2 reduction. It is found that the high‐quality interface in heterojunction and anisotropic charge transfer of CdZnS nanorods (NRs) enable efficient spatial separation of charge carriers in CsPbBr3–CdZnS heterojunction. The CsPbBr3–CdZnS heterojunction achieves a higher CO yield (55.8 µmol g−1 h−1) than that of the pristine CsPbBr3 NCs (13.9 µmol g−1 h−1). Furthermore, spectroscopic experiments and density functional theory (DFT) simulations further confirm that the suppressed recombination of charge carriers and lowered energy barrier for CO2 reduction contribute to the improved photocatalytic activity of the CsPbBr3–CdZnS heterojunction. This work demonstrates a valid method to construct high‐quality heterojunction with directional charge transfer for photocatalytic CO2 reduction. This study is expected to pave a new avenue to design perovskite–chalcogenide heterojunction.

CdS/ZnSnO3 Hollow Core–Shell Nanocubes for Photocatalytic Hydrogen Evolution and Degradation of Ciprofloxacin

“…As revealed, the diffraction peaks at 33.98 and 59.36° are ascribed to the (100) and (120) planes of ZnSnO 3 (PDF#89-0095, Figure S1), − and are consistent with the samples with Sn 2+ self-doping and CdS deposition, indicating that the Sn 2+ ion self-doping would hardly influence the crystalline structure and the ZnSnO 3 owing to its decent stability during the surface heterojunction deposition. ,, With deposition of the CdS nanoshell, the new diffraction peaks at 25.45, 26.90, 28.34, 44.12, and 52.36° are ascribed to the (100), (002), (101), (110), and (112) planes of CdS (PDF#41-1049). − Interestingly, all diffraction peaks exhibit obvious broadening, which can be ascribed to the minuscule grain size of the CdS nanoshell. No other peaks can be observed, indicating that the nanostructure is mainly composed of ZnSnO 3 and CdS.…”

“…As shown by SEM, the CdS/Sn 2+ -ZnSnO 3 heterojunction (Figure a) reveals a typical hollow core–shell cubic structure; especially, the CdS nanoshell can be observed clearly. As shown by HRTEM, the lattice spacings of 0.338 (Figure b) and 0.265 (Figure c) nm are ascribed to the (002) plane of CdS and (110) plane of ZnSnO 3 . − ,− In addition, EDX (Figure S4) manifests the presence of Cd, Zn, and Sn elements and can be supported by the corresponding element mapping (Figure d–f). As shown, the distributions of Cd, Zn, and Sn elements show a hollow core–shell cubic structure, which corresponds to the as-prepared CdS/Sn 2+ -ZnSnO 3 heterojunction.…”

“…The carrier behaviors of the CdS/Sn 2+ -ZSO heterojunction are demonstrated in Figure . There, the photocurrents (Figure a) correspond to the photocatalytic performances and increase remarkably to ∼8.85 × 10 –7 A (Sn 2+ -ZSO), ∼1.01 × 10 –5 A (CdS/Sn 2+ -ZSO-3), and ∼5.24 × 10 –6 A (CdS/ZSO-3), much higher than those of single ZSO (∼4.13 × 10 –7 A) and CdS (∼1.45 × 10 –6 A), manifesting that the introduction of Sn 2+ /O v and formation of heterojunction can promote the carrier separation/transportation effectively. − Supported by the EIS Nyquist plots, the decreased impedance of the CdS/Sn 2+ -ZSO heterojunction indicates the ameliorative carrier interface diffusion/immigration (Figure b). − Furthermore, the high carrier recombination leads to effective inhibition, as revealed by the PL (Figure c), which is decreased because of the efficient carrier separation. The decreased extremum in the Bode plots (Figure d, τ n = 1 2 π f m ) manifests that the CdS/Sn 2+ -ZSO heterojunction can prolong the carrier lifetime effectively via inhibiting carrier recombination and promoting the carrier interface diffusion. ,, As evaluated by the TRPL (Figure e), the corresponding lifetimes of Sn 2+ -ZSO, CdS/Sn 2+ -ZSO-3, and CdS/ZSO-3 are ∼1.76, 22.87, and 5.11 ns, much longer than those of single ZSO (∼1.57 ns) and CdS (∼2.06 ns).…”

“…The HRXPS images are used to confirm the components of CdS/Sn 2+ -ZnSnO 3 , especially to confirm the introduction of Sn 2+ self-doping and concomitant O v . The peaks at 404.90 and 411.65 eV are from Cd 2+ (Figure a) and those at 161.28 and 162.44 eV are from S 2+ (Figure b), which manifest the deposition of the CdS nanoshell. − The peak at 167.98 eV is from the surface unsaturated S atoms and is deemed as an active site due to the quick carrier transfer. − The peaks at 1021.44 and 1044.48 eV are from Zn 2+ (Figure c) and those at 486.28 and 495.03 eV are from Sn 4+ (Figure d), which manifest the formation of ZnSnO 3 . − Significantly, compared with the sample without Sn 2+ doping (CdS/ZnSnO 3 , Figure S5), the extra peaks at 485.08 and 494.04 eV are from Sn 2+ , and combined with Figure e, the peaks at 529.86, 531.04, and 532.00 eV are from the Sn–O bond, the O v associated with Sn 2+ , and surface-absorbed water, respectively, manifesting the successful achievement of Sn 2+ cation self-doping and O v synergistic concomitance. − ,− The mixed Sn 2+ /Sn 4+ state can increase the carrier concentration and O v can induce a shallow donor level for increasing the solar efficiency, both of which are beneficial for the intrinsic charge carrier quickly transferring and diffusing. ,− Herein, the Sn 2+ ion self-doped CdS/ZnSnO 3 hollow core–shell cubic heterojunction is formed.…”

“…For ZSO, owing to the wide optical band gap, it exhibits only ultraviolet light response and the corresponding optical band gap is 3.973 eV (Figure S9a,b). − With Sn 2+ self-doping, owing to its stable crystalline structure and shallow donor level, the optical band gap of Sn 2+ -ZSO decreases to 3.872 eV. − Significantly, the increased photocatalytic performance is much higher than the increased light response, including the HER and CIP degradation, indicating that the carrier behavior regulation caused by the shallow donor level and complex electronic structure of O v would play more important roles. − With deposition of CdS, the absorption edge exhibits a remarkable red shift and the corresponding optical band gap of CdS/Sn 2+ -ZSO (CdS/Sn 2+ -ZSO-3) is 2.767 eV, which is the median of CdS (the optical band gap of CdS is 2.332 eV) and Sn 2+ -ZSO. − Similarly, the increased photocatalytic performance is much higher than the increased visible-light response, indicating that the carrier behavior regulation caused by the heterojunction would be the decisive factor instead of the simply increased absorption.…”